The most profound change in music over the past century was the shift from acoustical to electronic technology. One hundred years ago all music was live, the phonograph was a primitive curiosity and radio was unknown. Today, nearly all our music is recorded or broadcast, pop is infused with synthetic sounds and even live theatre comes to us amplified and enhanced.

That wasn't my original thought; rather it's part of Brian Eno's introduction to OHM, an outstanding 3-CD box from Ellipsis Arts that presents, as the subtitle puts it, the early gurus of electronic music. It's a fine package - compact and attractive, with brief but revealing notes by its 42 composers. If you can't find it in stores, it can be ordered directly from ellipsisarts.com. It's fascinating and, for only $40, quite a bargain.

The set wisely avoids the electronic product we already know well (synthesizers, sampling, techno), and instead explores the crucial formative years of the genre. The focus is on artistic results rather than the technology that makes it all possible, and that's an essential distinction. The mere creation of funny noises or the replication of sounds humans already make may be an impressive technological feat, but not an artistic advance. But more of that in a moment... .

First, some background. Electronic music is often snubbed by the cultural elite as an oxymoron, but it's really an integral part of the course of musical development that began at the dawn of our cultural history, when early man first tried to complement the human voice with a primitive instrument. Once our forbears responded to a string or reed vibrating with a quality different from a larynx, the trend was underway. Even once instrumental music was firmly established on its own, composers often sought to extend conventional sound by imitating nature (Vivaldi's Four Seasons, Beethoven's Pastorale Symphony) or by adding sound effects (funeral gongs in Berlioz's Symphonie Fantastique, anvils in Wagner's Das Rheingold). The next step was to incorporate non-natural sounds into traditional music (a wind machine in Ravel's Daphnis et Chloe, airplane propellers and sirens in Antheil's Ballet Mechanique). The culmination was to replace acoustical instruments altogether. That's where OHM begins.

The artistic phase of the evolution from natural to electronic instruments is perhaps best known through the development of the guitar over the last century. The basic instrument is heard as mere accompaniment in the earliest folk and blues records. In the 1930s, the electrified version enabled the guitar to assume a commanding solo spot. Its new power and prominence were typified by Charlie Christian (in the Benny Goodman band) and Leon McAuliffe (with Bob Wills' Texas Playboys), but while they surely expanded the expressive vocabulary of their instrument with a crisp attack, commanding tone and ringing decay, their playing still largely resembled the unplugged version. Les Paul's tape experiments with speed, echo and multitracking took the guitar to a new creative level, but such techniques typically provided a convenient way for an individual artist and his technicians to replicate a virtuoso ensemble and still sounded mostly familiar. It was with the feedback and distortion of Jimi Hendrix that a wholly new concept emerged - a type of expression that liberated the guitar from its acoustical roots to create a genuinely novel instrument that transcended anything heard in nature and thus vastly expanded the realm of creative uses to which it could be put.

Electronic music in general followed a similar progression. The first true electronic instrument was built in Russia in 1920 by Leon Theremin, who immodestly dubbed his creation the theremin. Its oscillating circuit consists of an induction coil and a capacitor, between whose plates graceful hand gestures determine both pitch and volume of a swooping warble familiar from the Beach Boys Good Vibrations and innumerable sci-fi soundtracks (starting in 1952 with Louis and Bebe Barron's Forbidden Planet). Although quaint and rudimentary nowadays, the theremin played a crucial role as the very first electric instrument that didn't merely emulate acoustical forebears and instead produced sounds previously unheard. Technology spawns art at the very point where it generates meaning that could not have been produced othewise.

Next came musique concrete, created in the studio by capturing and manipulating natural sounds. The first such piece was Pierre Schaeffer's 1948 Etude aux Chemins de Fer, which used records with looped rather than spiral grooves to repeat and combine railroad sounds into new rhythmic patterns.

The greater editing possibilities of tape soon supplanted discs. Aside from toying with phase distortion (playing two tracks of the same sound slightly out of sync to alter overtones, introduced in Tony Fisher's 1959 The Big Hurt), producers were content to use tape mostly for purposes of rudimentary sampling, mixing multiple tracks and constructing note-perfect performances out of multiple takes. There was only slight creativity in these applications, which did little more than control and polish sounds that already resembled live performance. Serious composers, though, seized upon the new medium of tape for precise juxtapositions impossible in real time. John Cage's 1952 Williams Mix required that pieces of tape be recorded, cut and assembled according to 500 pages of painstakingly exact instructions. As with so much of Cage's work, though, the concept was more impressive than the result, which belies its rigorous concept and sounds like a random mess.

Finally, the electronic music scene was transformed by analog and then digital computers, which made all these things (and more) both possible and relatively simple. At long last, for the first time in the history of mankind, any sound conceivable could be realized and manipulated without limit. Yet, the vastly expanded opportunity created an even greater challenge - to apply artistic restraint and wisdom to select from the infinite possibilities those elements apt to create meaning and evoke a genuine human response.

And that brings us to OHM, which provides not only the seminal works noted above, but the opportunity to hear how a variety of artists seized upon the unfettered creative potential of the electronic medium. Here's a brief tour. Although the set is presented chronologically, I've tried to reorganize the contents by a more conceptual approach:

Established Composers - Electronics attracted mostly a new breed of composer, unfettered by conventions of the past. The principal exception was Edgard Varese who, in the apt words of Harold Schonberg, was writing electronic music before there was any such thing. In the 1920s his sonic innovations had expanded the orchestral range with percussion and massed sounds but then Varese became frustrated with the limitations and abandoned composing. In a last work, the 1958 Poem Electronique, he finally realized his ideal of creating music from the natural attributes of sound.

Traditional Uses - The most basic use of electronics is simply to treat the computer as a traditional instrument and to integrate it into a conventional model. Many works reveled in the sheer novelty of innovative sounds and the joy of producing them. Richard Maxfield's Sine Music, Raymond Scott's Cindy Electronium and Osckar Sala's Elektronische Tanzsuite use synthesizer sounds to emulate the minimalism of Webern, the bounding spirit of baroque and the pleasure of light romantic music. Milton Babbitt's Philomel is far more subtle, a careful construct of live and taped voices and keyboard to shape a seemingly spontaneous, albeit strictly ordered, performance.

Multi-tracking - Among the first inherent attributes of electronics to be exploited was the ability to layer and extend single inputs into longer forms. Hugh Le Caine's Dripsody multiplies the sound of a single drop of water thousands of times to generate a kaleidoscope of tone and rhythm. Otto Luening's Low Speed deconstructs a flute into overlays of its pulsing, reverberent overtones; Terry Riley's Poppy Nogood multiplies saxophone figurations; Paul Lansing's Six Fantasies on a Poem by Thomas Campion fashions a richly-harmonized a capella vocal sound; Alvin Curran's Canti lIlluminati crafts a wall of sound from microtonal variations of a single voice.

Fragmentation - The most basic property of tape is its ability to be edited. Most editing achieves a practical purpose of piecing together a cohesive performance from fragmentary takes. A more fascinating use arises in Charles Dodge's brief He Destroyed Her Image, in which fragments of a poem are turned into music by altering and editing individual syllables and sounds. The text becomes comprehensible simultaneously on two separate levels - the verbal meaning of the words and the abstract pattern of sound.

Timbre - All musicians alter the sheer sound of the vocal and instrumental tones they produce for expressive effect. A sophisticated artistic use of electronics is to expand and permit complete control over this process. In John Chowning's Sitra tone colors gradually evolve, and in Jean-Claude Risset's Mutations discrete notes melt into sweeping glissandos, while Morton Subotnick's Silver Apples of the Moon is a moto perpetuo of wildly diverse timbres.

Atmosphere -Extending the approach of musique concrete, two works go beyond recordings of natural sounds to create wholly new ones that achieve the wondrous result of being especially evocative. Joji Yuasa's Projection Esemplastic for White Noise consists of graceful soaring sounds that suggest supernatural winds (or, as Yuasa puts it, an internal expression like a snowstorm in one's mind). Brian Eno's Unfamiliar Wind (Leeks Hill) seeks to recreate the sounds and feel of a forest where he played as a boy.

Architecture - Spatial music is nothing new - Handel's Water Music positioned players on river barges and Berlioz's Requiem used quadraphonic brass choirs - but the complexities of more ambitious coordination are abetted by computers. The two speakers of a stereo are a natural starting place for electronic experimentation - sadly so in those awful two-channel versions of early rock songs (vocals on the left, everything else on the right), but far more creatively here in Laurie Spiegel's Appalachian Grove and Bernard Parmegiani's En Phase/Hors Phase, which create lyric patterns by shuttling sharp, pointed sounds abruptly between the stereo channels; the former is deliberately limited in its sonic palette while the latter is seasoned with complementary events. Luc Ferrari's Music Promenade goes quad with an encounter among tapes of European insects, water and machinery played from the four corners of a concert hall. Maryanne Amacher's Music for Sound-Joined Rooms goes even further by using the echos and resonances of an entire house coming alive with sound cascading through its rooms (although most of the effect is lost in this two-channel remastering).

Social Activity - A human sort of architecture is found in Cage colleague David Tudor's Rainforest Version I, a festive celebration in which a huge variety of everyday objects are made to vibrate with transducers. While the participants undoubtedly had fun, the audio record of the live event conveys little of its essence.

Computers as Composers - Long before the dawn of PCs, sci-fi writers fueled fascination and fear that one day robots and computers would become human and perhaps even usurp us. David Berhman's On the Other Ocean presents an intriguing early step in that process, as computers interact with and shape the course of a live performance. As Berhman explains it, when a live performer plays a certain pitch it triggers a computer which can sense the order and timing and then reacts by sending harmony-changing messages to a synthesizer. Thus, the musicians and the computer interact, with the computer changing the electronically produced harmonies in response to what the musicians play, and the musicians influenced in their improvising by what the computer does.

Conceptual Purity - Three works are deliberately and drastically simplified in their concept and execution. La Monte Young's 31/69 c.12:17:33-12:24:33 PM NYC consists of a single seven-minute sine tone in each stereo speaker in a 30:31 ratio, the quality and intensity of the beat frequency varying as you move through your listening area. Alvin Lucier's Music on a Long Thin Wire presents the lingering resonances of an oscillated tuned wire. Steve Reich's Pendulum Music provides the rhythmic feedback of four microphones suspended and swung over speakers, the sound ending as a complex drone when they all come to rest. All three pieces are relaxed, confident, eloquent and self-effacing. Some listeners will find them brilliantly focused and fascinating; others just annoying.

Overload - At the extreme opposite end of the spectrum are two works of overwhelming complexity. The MEV collective's Spacecraft tosses together a huge range of inputs and subjects them to extreme amplification and distortion. It's a self-described attempt to "dissolve barriers between individual egos and range them into a collective consciousness" but while purporting to be "open and eclectic," the result is mostly noise. It's somewhat like blending together every known color - in place of beautiful hues you just wind up with dark murk. Reportedly, performances of this piece lasted up to six hours and perhaps the cohesion lacking in this excerpt emerges over time. There's also Iannis Xenakis's Hibiki-Hana-Ma - Western and Japanese instruments splayed among 12 channels and 800 speakers to represent transcending pain "into that hypothetical place where all aspects of human nature can be celebrated." Somehow, though, there's something amiss with music that needs to be explained to make sense.

Self-Indulgence - Also far removed from the modesty of Young, Lucier and Reich are works that seem to be an artist's impenetrable private fantasy. Robert Ashley's Automatic Writing consists of a girl whispering French over distant tapping and a walking bass, an interior monologue Ashley was living with at the time. Pauline Oliveros's Bye Bye Butterfly plays an opera record over an existing tape of various random sounds. Holger Czukay's Boat-Woman-Song combines lush medieval vocals with two nasal folk songs, which the composer views as a fascinating idea of combining two incompatible cultures. With all due respect, I find all three far more interesting as verbal ideology than sonic realization. All great art is deeply personal, but there's a point at which individual inspiration is able to express universal truth, and I'm just not sure it happens here.

Maturity - Last and certainly not least, having explored and often been carried away by the intoxicating possibilities of electronic music, having sown their wild oats as it were, electronic composers already have begun to produce mature art in which the elements are chosen and combined to create music that is innovative and wondrous, albeit highly unconventional. In Klaus Schulze's Melange, Jon Hassell's Before and After Charm (La Notte) and, above all, Karlheinz Stockhausen's Kontakte, rhythm, tones, timbres and a sense of space are combined to summon deeply emotional and richly evocative imagery. To me, these works validate the entire field of electronic music, as they extend and supplant traditional elements and techniques while preserving the ultimate purpose of art - to stir a human response that arises out of yet transcends the properties and meaning of the actual materials.

Two more observations. First, we often think of computers as the province of the young. (After all, how many parents approach the intuitive computer savvy of their kids?) Yet, only one of the 42 pieces in OHM was written by a composer under 30 (and she was 29!). Many were the product of artists well past the age when the appeal of new ideas is assumed to have ceased.

Second, OHM measures how far we've come in the 20 years since completion of its most recent work. A mere generation ago, pioneers struggled over a single short piece for years with techniques that have become simple matters with current technology. Rudimentary programming and routine processing power now can achieve in hours what the four minutes of Williams Mix took Cage and his crew a year to prepare.

But the blinding speed with which electronic music has progressed since the era of OHM carries a risk. Great art requires intense commitment and significant struggle. The sheer amount of effort required of the electronic pioneers (and their acoustical predecessors) forced them to carefully plan and craft every detail of their work. The relative ease of pushing a few keys nowadays can foster a careless, casual attitude. The result all too often can be a vapid and disposable product that denies the essential purpose of artistic creation.

Ultimately, then, OHM presents an absorbing irony and challenge - despite the vastly greater resources of modern technology, how many contemporary pieces are apt to outlast the pure majesty of Bach? While progress has enriched our lives in so many ways, something human can easily be lost.